This invention relates to apparatus for measuring combustion chamber pressure in an end burning grain solid propellant rocket, and more particularly to apparatus suitable for making such measurements under actual flight conditions.
It has been usual to measure rocket combustion chamber pressure in static rocket firings by tapping the combustion chamber pressure at the rocket nozzle plate using apparatus mounted external to the rocket. This method is not practical when testing a rocket which must be launched from a gun bore or tested under actual flight conditions.
Any apparatus external to the rocket would interfere with the gun barrel or with the rocket flight characteristics and would be difficult to retain to the exterior of an accelerating rocket. Other methods used to measure combustion chamber pressure have involved casting pressure pickup tubes into the propellant grain during manufacture, thereby allowing the pressure sensing equipment to be carried inside the rocket. This method, however, does not permit testing rockets which have been previously manufactured without specially molded in pressure sensing tubes. Adding pressure sensing tubes to all rocket propellant grains is not desirable because doing so increases the chance of rocket malfunction. The tube-grain interface could become the source of grain unbonds, resulting in improper grain burning and rocket motor catastrophic failure. Also, integral pressure tubes displace propellant volume, reducing range or thrust.